When I go into creative mode I only seem to find the Aether dragon egg and no other breeds' eggs. Same goes for in the JEI. I am on 1.20.1, originally installed Better MC 4 forge and then downloaded Dragon Mounts Legacy mod file again and replaced it and it still gives the same problem

Did you find a solution to this? I'm having the same problem. When I go in creative I can only seem to find the Aether dragon egg and no others, like fire, forest, ice, water, etc. If you could help me out I would greatly appreciate it.

So there is only aether eggs originally, if you want to other type eggs you will have to convert the aether egg to the respective egg. Go to their documentation website and they have stated what are the things to do to convert the egg